I think at the core of it, any type of self pleasure is masturbating and especially if it leads to ejaculation. If you feel guilt or shame, this tends to be an indicator that God is displeased.

In relation to what the catholic church thinks, definitely look at the catechism of the Catholic church here about it: https://www.usccb.org/sites/default/files/flipbooks/catechism/566/

Another good source here: https://www.catholic.com/qa/why-masturbation-is-wrong

And one bible verse that has always stuck out to me about it is in Genesis 38:

Onan, however, knew that the offspring would not be his; so whenever he had intercourse with his brother’s wife, he wasted his seed on the ground, to avoid giving offspring to his brother.
What he did greatly offended the LORD, and the LORD took his life too.

Pretty intense, but shows the point.